Vertical cylindrical silo with wall of flexible material

ABSTRACT

This disclosure teaches a silo having a vertical cylindrical wall of a flexible material, preferably of textile fabric suspended from a supporting frame and preferably engaged sealingly to a rigid lower closure. The flexible material, such as the textile fabric is wound in a spiral band with its lower margin connected to the upper margin of the last preceding turn to form the vertical cylindrical wall of the silo. By this expedient vertical seams are avoided so that weft threads of the textile fabric are substantially spared from tangential hoop stresses. The textile fabric is preferably woven and coated with rubber or plastic.

United States Patent Lieckfeld [45] May 23, 1972 541 VERTICAL (IYLINDRICAL SILO WITH 2,943,752 7/1960 1 1m ..52/197 x WALL OF FLEXIBLE MATERIAL 2,852,110 9/1958 Dueringer ....52/247 X 2,866,261 l2/1958 Macku ..220/] B X [72] Invent Werner Leckfeldi Stem/Tam, 2,378,159 6/1945 Royer ..22o 1 B many 3,380,147 4/1968 McDonald .52/745 x [73] Assi n Bra & L bb H b Germany 2,407,455 9/1946 Shakesby et a1. ..220/7l [223 Filed: 1970 Primary ExaminerPrice c. Faw, Jr. [21] A l, N 32,118 Attorney-Erich M. Radde, Charles A. McClure, Gerard J.

Weiser and Alfred Stapler [30] Foreign Application Priority Data 57 ABSTRACT 1969 Germany 19 21 512'4 This disclosure teaches a silo having a vertical cylindrical wall of a flexible material, preferably of textile fabric suspended [52] US. Cl 119524, ZZZ/(2)22, from a supporting frame and preferably engaged scaling), to a 51 l t Cl i l rigid lower closure. The flexible material, such as the textile id 263 5 194 fabric is wound in a spiral band with its lower margin con- Ie 22; "222 220/} 12 1 7 nected to the upper margin of the last preceding turn to form the vertical cylindrical wall of the silo. By this expedient vertical seams are avoided so that weft threads of the textile fabric are substantially spared from tangential hoop stresses. The [56] References cued textile fabric is preferably woven and coated with rubber or UNITED STATES PATENTS p 278,957 6/1883 Heft ..l38/l54 21 Claims, 4 Drawing Figures lllllll lll) Patented Ma 23, 1972 3,664,072

3 Sheets-Sheet 'l Patented May 23,1972 3 3,664,072

3 Sheets-Sheet 5 FIG. 4

INVENTOR. WERNER L/EC/(FELD VERTICAL CYLINDRICAL SILO WITH WALL OF FLEXIBLE MATERIAL BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silo that is transportable readily and more particularly to a collapsible silo of flexible material preferably textile fabric, to be used for receiving, storing, and discharging by gravity free-flowing, loose bulk materials.

2. Description of the Prior Art Various attempts have been made to make readily transportable vertical cylindrical silos (or storage bins) with a wall of a textile fabric so as to avoid difficulties encountered in transporting silos with walls made of metal or wood and to achieve space savings when these silos are empty. According to one known type of construction the wall of the vertical cylindrical silo is made of annular panels of the textile fabric arranged one above the other and with the panels having a height which corresponds to the width of the textile fabric. Said annular panels are sewn or welded together. (It should be noted that a like flexible material may be used in lieu of the textile fabric.) In such silos, however, seams run horizontally and vertically on the cylindrical wall. According to known techniques of stress analysis, tangential tensile stresses on the cylindrical wall under internal pressure are approximately twice as high as the axial forces on that wall; therefore, the vertical seams are subjected to especially high tensile stresses thereacross. As a result of high tensile stresses on the vertical seams, the strength and durability of such cylindrical silos with walls of textile fabrics are limited.

Vertical cylindrical silos have also been made with a wall of vertical strips of textile fabric or like flexible material arranged side by side. In the case of these vertical strips, only the vertical seams are present in the cylindrical wall wall of the silos; accordingly, the strength and durability of these silos has not proven to be satisfactory because the vertical seams are especially vulnerable to the tangential tensile stresses.

Furthermore, silos have been manufactured from seamless tubular textile fabrics or like flexible material with the lower part tapered off by providing wedge-shaped folds or pleats. Here again in these silos the greatest stress is tangential, and even though there are no vertical seams, the fabric is subjected to these tangential forces in its weft direction which is least capable of withstanding these forces.

It should be understood that in weaving textile fabrics, a distinction is made between warp and weft depending upon the arrangement of the loom. While warp threads are kept under uniform tension during weaving, it is not possible to keep the tension on the weft threads uniform. As a result of the foregoing, the resistance to tearing of the textile fabric is distinctly higher in the direction of the warp threads than in the direction of the weft threads. Also, when coating fabrics it is not always possible to maintain accurately the setting in the weft direction when coating the fabric. Coating procedures are usually carried out at elevated temperatures and as a result thereof the fabrics may shrink more or less but usually more in the weft direction due to the high temperature. These two causes are additively responsible for the fact that stretching of coated textile fabric in its weft direction can be up to times the stretching of the same textile fabric in its warp direction. The resistance to tearing of the textile fabric is also distinctly higher in its warp direction than in its weft direction.

If the wall of the silo is sewn or welded, the stress to which the textile fabric can be exposed without tearing may be still further reduced by relatively low carrying capacities of such seams.

SUMMARY OF THE INVENTION It is one object of the present invention to provide a readily transportable silo having a vertical cylindrical wall of a textile fabric and having neither vertical nor horizontal seams and in which the tangential stresses in the cylindrical silo wall are substantially completely resisted by warp threads.

In principle the problem forming the basis of the present invention is solved by providing a vertical cylindrical silo with a wall of textile fabric or like flexible material which comprises one or several bands of said textile fabric arranged spirally and spirally welded, sewn, glued, or otherwise firmly attached to each other to form a unitary cylindrical wall.

According to a preferred embodiment of the present invention a lower discharge funnel is made of rigid material for supporting bulk materials in the silo.

The vertical cylindrical wall of the silo according to the present invention is suspended from or mounted on a structural supporting frame, scaffold, rack, tripod, or the like. The silo can be composed of several parts, for instance, of the cylindrical wall, a lower discharge funnel, and an upper feeding funnel and/or cover. In this manner a silo is provided which can be moved and transported as well as assembled and dismantled readily and which is of greater strength and stability than those of the prior art.

The discharge funnel, to which the cylindrical wall is connected, is preferably made of steel. A major portion of the vertical component of the weight of bulk material stored in the silo is resisted by said rigid discharge funnel. Thus predominantly, tangential hoop stresses are imposed on the silo wall. Magnitudes and orientations of said stresses are a function of the weight and other characteristics of the bulk material as well as the slope of the funnel.

BRIEF DESCRIPTION OF THE DRAWING The present invention will be understood more thoroughly by a consideration of the following detailed description of a preferred embodiment thereof illustrated in the attached drawing, wherein FIG. 1 is an elevation view of a vertical cylindrical silo according to the present invention,

FIG. 2 is an elevation view showing a preferred supporting frame, and

FIG. 3 is a plan view corresponding to FIG. 2.

FIG. 4 is an elevation view of a vertical cylindrical silo according to the present invention with a plurality of bands alternating in sequence.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In said FIGS. 1 to 3 the vertical cylindrical silo wall 3 is made of a single width or band of textile fabric 2 which is wound spirally to form the silo wall. The lower margin of textile band 2 is sewn to the upper margin of the preceding winding of the band. Spirally ascending seam 7 which may be sewn or welded or even glued is shown distinctly in the figures. The cylindrical wall is suspended at its upper end from a supporting fame generally designated 6 and is connected at its lower end in sealing engagement to funnel or lower closure 4 of a rigid material such as steel. Funnel 4 rests on and is supported by vertical props 1. The major portion of the weight of bulk materials in the silo is supported by rigid funnel 4. The silo is provided at its top with cover 5.

The material composing wall 3 is preferably a band of woven textile fabric which may be provided with a coating of rubber, plastic, or the like material.

Supporting frame 6 is shown in greater detail in FIGS. 2 and 3. Props 1 support lower ring 8 from which lower closure 4 with annular spout 9 depend. Sleeves l0 and are spaced peripherally about lower ring 8 to receive columns 11 therein for mounting. Columns 11 support upper ring 12 which carries cover 5 and spokes 13 to hold upper funnel 14 in position. Diagonal bracing 15 and girth members 16 complete enclosure of wall 3. Alternating sleeves are provided with cranks 17 for engaging their associated columns for adjustment.

According to the preferred embodiment of this invention, as illustrated in FIGS. 1 to 3, a band of rubber or plastic coated textile fabric of a width of, for instance, about 50 cm. is used. The wall 3 is formed from such a band by winding it spirally upwardly and connecting each lower margin of said band to the upper margin of the preceding winding by sewing thus forming a spirally running continuous sewn seam 7. Said seam has a gradient or rise of preferably between about 3 percent and about 1 1 percent and most advantageously between about 5 percent and about 6 percent. Due to such a slow rise the tangential stresses to which the sewn seam is subjected are taken up almost completely by the warp threads of the textile fabric and no substantial vertical stress across the seam is created. The gradient or rise of spirally running seam 7 is preferably related to the width of the fabric and the circumference of the silo according to the following formula:

tan =(b/d-1r) whereby b is the width of the fabric and dis the diameter of the silo. The following table indicates the gradient or rise in percentage Diameter Width Gradient Width Gradient of Fabric of fabric d b mm. mm. mm. 2200 500 7.2 750 10.8 2700 500 5.9 750 8.8 3500 500 4.5 750 6.8 4100 500 3.9 750 5.8 5000 500 3.2 750 4.8

It is also possible to use several widths or bands of textile fabric or like flexible material and to wind said widths or bands one upon the other so as to form the cylindrical wall.

In said FIG. 4, three bands 2a, 2b, 2c are offset circumferentially relative the vertical cylindrical silo wall 3 each by 120.

I claim:

1. A vertical cylindrical silo for a pourable nonliquid material and comprising in combination:

a lower closure made ofa rigid material,

a supporting frame mounted above the lower closure,

a flexible woven textile fabric having a warp direction and a weft direction and organized in a relatively long continuous band in the warp direction,

a vertical cylindrical wall formed from the band wound in a continuous spiral free of any substantially vertical seams in weft direction,

the band having a lower margin and an upper margin with the lower margin connected to the upper margin of the last preceding turn of the spiral to form a continuous substantially horizontal seam in warp direction,

the wall depending from the supporting frame,

the wall connected in sealing engagement with the lower closure,

means for introducing and withdrawing the material respectively into and out ofthe silo.

2. The silo of claim 1 and the textile fabric organized in a plurality of bands,

each of the bands parallel to the other with their turns alternating in sequence.

3. The silo of claim 2 and the woven textile fabric coated with a suitable impermeable material.

4. The silo of claim 3 and the woven textile fabric coated with rubber.

5. The silo of claim 3 and the woven textile fabric coated with plastic.

6. The silo of claim 3 with a cover mounted above the wall and connected in sealing engagement therewith.

7. The silo of claim 3 with the spiral seam having an ascending gradient of from about 3 percent to about l l percent.

8. The silo of claim 3 with the spiral seam having an ascending gradient of from about 5 percent to about 6 percent.

9. The silo of claim 3 with the lower margin of the band sewn to the upper margin of the preceding turn.

10. The silo of claim 3 with the lower margin of the band welded to the upper margin of the preceding turn.

11. The silo of claim 3 with the lower margin of the band glued to the upper margin of the preceding turn.

12. The silo of claim 1 and the woven textile fabric coated with a suitable impermeable material.

13. The silo of claim 12 and the woven textile fabric coated with rubber.

14. The silo of claim 12 and the woven textile fabric coated with plastic.

15. The silo of claim 12 with a cover mounted about the wall and connected in sealing engagement therewith.

16. The silo of claim 12 with the spiral seam having an ascending gradient of from about 3 percent to about 1 l percent.

l7. The silo of claim 12 with the spiral seam having an ascending gradient of from about 5 percent to about 6 percent.

18. The silo of claim 12 with the lower margin of the band sewn to the upper margin of the preceding turn.

19. The silo of claim 12 with the lower margin of the band welded to the upper margin of the preceding turn.

20. The silo of claim 12 with the lower margin of the band glued to the upper margin of the preceding turn.

21. A vertical cylindrical silo for a pourable nonliquid material and comprising in combination:

a lower closure made of a rigid material,

a supporting frame mounted above the lower closure,

a flexible fabric having a warp direction and a weft direction and organized in a relatively long continuous band in the warp direction,

a vertical cylindrical wall formed from the band wound in a continuous spiral free of any substantially vertical seams in weft direction,

the band having a lower margin and an upper margin with the lower margin connected to the upper margin of the last preceding turn of the spiral to form a continuous substantially horizontal scam in the warp direction,

the wall depending from the supporting frame,

the wall connected in sealing engagement with the lower closure,

means for introducing and withdrawing the material respectively into and out of the silo. 

1. A vertical cylindrical silo for a pourable nonliquid material and comprising in combination: a lower closure made of a rigid material, a supporting frame mounted above the lower closure, a flexible woven textile fabric having a warp direction and a weft direction and organized in a relatively long continuous band in the warp direction, a vertical cylindrical wall formed from the band wound in a continuous spiral free of any substanTially vertical seams in weft direction, the band having a lower margin and an upper margin with the lower margin connected to the upper margin of the last preceding turn of the spiral to form a continuous substantially horizontal seam in warp direction, the wall depending from the supporting frame, the wall connected in sealing engagement with the lower closure, means for introducing and withdrawing the material respectively into and out of the silo.
 2. The silo of claim 1 and the textile fabric organized in a plurality of bands, each of the bands parallel to the other with their turns alternating in sequence.
 3. The silo of claim 2 and the woven textile fabric coated with a suitable impermeable material.
 4. The silo of claim 3 and the woven textile fabric coated with rubber.
 5. The silo of claim 3 and the woven textile fabric coated with plastic.
 6. The silo of claim 3 with a cover mounted above the wall and connected in sealing engagement therewith.
 7. The silo of claim 3 with the spiral seam having an ascending gradient of from about 3 percent to about 11 percent.
 8. The silo of claim 3 with the spiral seam having an ascending gradient of from about 5 percent to about 6 percent.
 9. The silo of claim 3 with the lower margin of the band sewn to the upper margin of the preceding turn.
 10. The silo of claim 3 with the lower margin of the band welded to the upper margin of the preceding turn.
 11. The silo of claim 3 with the lower margin of the band glued to the upper margin of the preceding turn.
 12. The silo of claim 1 and the woven textile fabric coated with a suitable impermeable material.
 13. The silo of claim 12 and the woven textile fabric coated with rubber.
 14. The silo of claim 12 and the woven textile fabric coated with plastic.
 15. The silo of claim 12 with a cover mounted about the wall and connected in sealing engagement therewith.
 16. The silo of claim 12 with the spiral seam having an ascending gradient of from about 3 percent to about 11 percent.
 17. The silo of claim 12 with the spiral seam having an ascending gradient of from about 5 percent to about 6 percent.
 18. The silo of claim 12 with the lower margin of the band sewn to the upper margin of the preceding turn.
 19. The silo of claim 12 with the lower margin of the band welded to the upper margin of the preceding turn.
 20. The silo of claim 12 with the lower margin of the band glued to the upper margin of the preceding turn.
 21. A vertical cylindrical silo for a pourable nonliquid material and comprising in combination: a lower closure made of a rigid material, a supporting frame mounted above the lower closure, a flexible fabric having a warp direction and a weft direction and organized in a relatively long continuous band in the warp direction, a vertical cylindrical wall formed from the band wound in a continuous spiral free of any substantially vertical seams in weft direction, the band having a lower margin and an upper margin with the lower margin connected to the upper margin of the last preceding turn of the spiral to form a continuous substantially horizontal seam in the warp direction, the wall depending from the supporting frame, the wall connected in sealing engagement with the lower closure, means for introducing and withdrawing the material respectively into and out of the silo. 